MEXICO CITY — Weeks before Mexico’s presidential election, some of the country’s biggest companies issued dire written warnings to their employees, cautioning them not to be misled by dangerous populists.

They were thinly veiled admonitions about one candidate — the man who appears increasingly likely to become this country’s next president: Andrés Manuel López Obrador.

His rise is seen by his opponents as the greatest threat to Mexico since it embraced democracy and a free-market economy at the end of the 20th century. One chief executive warned of “catastrophic effects” in his letter to employees. Another said that the candidate’s proposals would “turn the clock back decades.”

López Obrador, a longtime fixture of the left and former mayor of Mexico City, holds a commanding lead in polls leading up to the July 1 vote, in large part because of an anti-corruption platform that has resonated with many lower- and middle-class Mexicans. “It’s an honor to be with Obrador,” his supporters scream at rallies.

But members of Mexico’s powerful private sector have suggested that López Obrador’s most dramatic policies could have devastating effects on the economy. Analysts and intellectuals say his lack of respect for Mexican government institutions could usher in a period of quasi-autocracy.

The stakes are high outside Mexico, too. The country is the United States’ third-biggest trading partner in goods, and its cooperation is crucial in the fight against drug trafficking. Mexico’s next president may inherit stalled negotiations on NAFTA, which the Trump administration is trying to alter to be more favorable to American workers.

Many Mexicans say the fear of a López Obrador presidency is overblown, and fanned by his political opponents. At this stage of the campaign, the candidate appears to be embracing a kind of centrism, courting some of the business leaders who had expressed concern about his ascent.

In recent weeks, López Obrador and his advisers met with global investment managers to offer their assurance that he is, at heart, an advocate of free trade and a strong private sector. Among his top advisers are millionaires who have contradicted some of the candidate’s policy positions, suggesting that private oil drilling contracts will not be dramatically affected, for example. But López Obrador has said that he won’t allow oil “to return to foreign hands.”

A man watches television screens showing López Obrador speaking during a presidential debate, at a restaurant in Merida, Mexico, on June 12, 2018. (Alejandro Cegarra/Bloomberg News)

Many observers of the election see two versions of López Obrador: one a pragmatist, like the popular, fiscally prudent politician he proved to be while governing Mexico City from 2000 to 2005; and the other an erratic populist, with proposals that could lead to economic turbulence.

Those include sharply increasing spending on social programs, imposing a cap on gasoline prices and putting the brakes on a 2013 reform to liberalize Mexico’s oil industry, which had long been a state monopoly.

“The future really depends on which López Obrador we get,” said John Padilla of IPD Latin America, a regional energy consultancy.

The candidate declined several interview requests from The Washington Post.

López Obrador has run for president twice before, and some see additional reasons to worry in the way he handled his narrow loss in the 2006 election. He held weeks-long protests in the center of Mexico City, declaring himself the country’s true president. He announced his disdain for the country’s courts and electoral system.

“The main concern about him is his democratic credentials. Will he govern as a democrat?” said Luis de la Calle, a former undersecretary in the Economy Ministry.

López Obrador has already promoted several institutional changes on the campaign trail. He will hold a referendum on his presidency after three years, stepping down if he loses, rather than fulfill the six-year term enshrined in Mexico’s constitution. Other pledges have been more theatrical: He won’t live in the presidential palace, or fly on the presidential plane (which he says he’ll sell to President Trump).

In this photo released by the National Electoral Institute (INE), presidential candidates, from left, Ricardo Anaya with the Forward for Mexico Coalition, Andres Manuel López Obrador with the Morena party, INE President Lorenzo Cordova Vianello, Jose Antonio Meade with the Institutional Revolutionary Party, and independent candidate Jaime Rodriguez, known as “El Bronco,” attend a debate in Merida, Mexico, on June 12. (Associated Press)

Those promises don’t flout Mexico’s democratic values, but a leader willing to depart from institutional norms could try to consolidate power, some say, much as the late president Hugo Chávez did in Venezuela. From 1929 to 2000, Mexico was ruled by a single party, the Institutional Revolutionary Party (PRI), and during much of that period the government played a major role in the economy and repressed the opposition. More than a leftist, some say, López Obrador could represent a return to that era.

“He’s not Chávez. He’s a 1960s PRIista,” said Luis Rubio, the president of the Center of Research for Development think tank, referring to members of the PRI.

But Mexico has changed dramatically since that era. The North American Free Trade Agreement brought an explosion of Walmarts, automobile factories and Burger Kings. A multiparty democracy has emerged. In 2013, Mexico’s Congress passed an energy-reform package that allowed foreign companies to drill for oil off its coast, a sharp departure in a country where petroleum reserves were long viewed as a nationalist symbol.

Hector Vasconcelos, a foreign policy adviser to López Obrador, said that unlike the historical Latin American left, which thinks that the United States is out to subjugate the hemisphere, “we don’t believe that.”

“We don’t want a confrontation with the United States,” said Vasconcelos, rumored to be a possible foreign minister if López Obrador is elected, adding that the campaign wants an “alliance for economic growth.”

A platform that some fear

In their pre-election letters to employees, several Mexican companies criticized some of López Obrador’s proposals, without naming him.

“We have recently heard worrying proposals of nationalizing companies, scrapping the energy and education reforms, among other ideas that would turn the clock back decades to an economic model that has been more than proven not to work,” wrote Germán Larrea, chief executive of conglomerate Grupo México. “Venezuela, Argentina, Cuba, the former Soviet Union, among others, are witness to that.”

Most analysts and diplomats say there’s little chance López Obrador will attempt to dramatically alter Mexico’s economic model. He has promised “no expropriations, no nationalizations.” But some of his constituents will certainly push for change.

In its “declaration of principles,” López Obrador’s Morena party wrote that the country’s “neoliberal model” has served “a true Mafioso state built by a minority that dominates political and economic power in Mexico.”

López Obrador greets supporters during a campaign rally in Uruapan, Mexico, on June 8. (Reuters/Reuters)

The biggest cheers that López Obrador receives at his massive rallies come in response to lines about the misdeeds of Mexico’s political elite. But his supporters are quick to say that López Obrador wouldn’t nationalize companies as authorities have done in Venezuela, which is suffering a severe economic crisis.

“Why would he be inspired by a country that’s a disaster?” said Marcelo Ebrard, a former mayor of Mexico City who supports López Obrador. “Give me a break.”

López Obrador has pledged to limit increases in fuel prices to the inflation rate and review oil and gas contracts signed under President Enrique Peña Nieto for signs of corruption. (Peña Nieto is constitutionally barred from running for reelection.)

López Obrador has a long history of activism regarding oil: His political career began in the 1970s in his native Tabasco state, where he led protests against the national oil company, Pemex, for not sharing more of its profits locally. He has said that Mexico should stop selling crude oil abroad, and instead develop its own refineries, a proposal that most energy experts say makes little economic sense.

“When it comes to energy, there’s rightfully concern to be had. And I think the first kind of moment of truth will likely be if he attempts to fulfill his promises on fuel price caps,” said Padilla, the energy consultant. “It would shake the overall confidence of investors, particularly in energy.”

Mexico is no stranger to economic crises caused by faulty government policies, suffering major devaluations in 1976, 1982 and 1994. For many Mexicans, particularly in the business community, those memories are guiding their fear of a López Obrador presidency.

“There are already guarantees of a crisis with López Obrador,” ran one headline in the newspaper El Economista in April.

Supporters use mobile phones to take photographs while López Obrador, not pictured, speaks during a campaign rally at night in Chilpancingo, Mexico. (Yael Martinez/Bloomberg News)

While López Obrador has proposed a range of new social programs — for the poor, the disabled, the elderly — he has spoken against increasing the country’s public debt. And he has promised not to increase taxes, even on Mexico’s wealthiest. His welfare programs, he said, would be funded by the money he saves by cracking down on corruption, an amount he estimates at $20 billion a year.

Many analysts are skeptical of that plan.

“Where’s this money going to come from? He says he’s not going to raise taxes, but where else do you get this amount of money? It’s a real question mark,” said Esteban Illades, the editor of Nexos, a cultural and political magazine.